杂谈 论实例化类的第六种方式

public class InstantialTest {
    private static Unsafe unsafe;    static {        try {            Field f = Unsafe.class.getDeclaredField("theUnsafe");            f.setAccessible(true);            unsafe = (Unsafe) f.get(null);        } catch (NoSuchFieldException e) {            e.printStackTrace();        } catch (IllegalAccessException e) {            e.printStackTrace();        }    }
    public static void main(String[] args) throws Exception {        // 1. 构造方法        User user1 = new User();        // 2. Class，里面实际也是反射        User user2 = User.class.newInstance();        // 3. 反射        User user3 = User.class.getConstructor().newInstance();        // 4. 克隆        User user4 = (User) user1.clone();        // 5. 反序列化        User user5 = unserialize(user1);        // 6. Unsafe        User user6 = (User) unsafe.allocateInstance(User.class);
        System.out.println(user1.age);        System.out.println(user2.age);        System.out.println(user3.age);        System.out.println(user4.age);        System.out.println(user5.age);        System.out.println(user6.age);    }
    private static User unserialize(User user1) throws Exception {        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("D://object.txt"));        oos.writeObject(user1);        oos.close();
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream("D://object.txt"));        // 反序列化        User user5 = (User) ois.readObject();        ois.close();        return user5;    }
    static class User implements Cloneable, Serializable {        private int age = 20;
        public User() {            this.age = 10;        }
        @Override        protected Object clone() throws CloneNotSupportedException {            return super.clone();        }    }}

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